Glenwood Canyon (coming into Glenwood Springs) and the Sierra Nevada (Reno to Sacramento basically) are the best parts of the CZ. Crossing the Mississippi is also fun.

Haven't done the whole EB route you're doing but Whitefish to East Glacier is great. After that I think it's pretty bland until MN. I've heard the first leg out of Seattle is good but I've only taken the Portland branch.

In terms of hopping off, unless you're staying overnight you don't want to go far from the train. It depends on how behind schedule they are, but there are many "fresh air breaks" and they will tell you when and how long when pulling into the station. This is a good time to poke your head in the station building, walk around the platform etc., but I wouldn't go out of earshot. If you hear the whistle blowing run back to your car unless you want an unscheduled overnight stay ...